In accordance with a rapid spread of information relevant apparatuses, communication apparatuses and the like such as a personal computer, a video camera and a portable telephone in recent years, the development of a battery to be utilized as a power source thereof has been emphasized. The development of a high-output and high-capacity battery for an electric automobile or a hybrid automobile has been advanced also in the automobile industry. A lithium battery has been presently noticed from the viewpoint of a high energy density among various kinds of batteries.
A liquid electrolyte containing a flammable organic solvent is used for a presently commercialized lithium battery, so that the installation of a safety device for restraining temperature rise during a short circuit and the improvement in structure and material for preventing the short circuit are necessary therefor. On the contrary, a lithium battery all-solidified by replacing the liquid electrolyte with a solid electrolyte layer is conceived to intend the simplification of the safety device and be excellent in production cost and productivity for the reason that the flammable organic solvent is not used in the battery.
An Li—La—Zr—O-based solid electrolyte material has been known as a solid electrolyte material used for an all solid state lithium battery. For example, in Patent Literature 1, a ceramic material containing Li, La, Zr, O and Al is disclosed. In Patent Literature 2, a method for producing a solid electrolyte structure using a ceramic material having a crystal structure of a garnet type or a garnet-like type composed of Li, La, Zr and O, and containing Al as a particle of a solid electrolyte is disclosed. In Patent Literature 3, an all solid state lithium battery provided with a solid electrolyte containing ceramics having a crystal structure of a garnet type or a garnet-like type composed of Li, La, Zr and O is disclosed. Further, in Patent Literatures 4 and 5, a lithium battery provided with a buffer layer containing Li7La3Zr2O12 between a cathode layer and a sulfide solid electrolyte layer is disclosed. In Patent Literature 6, a lithium-containing garnet-type oxide having a basic composition of Li7La3Zr2O12 is disclosed.